What is the appropriate workup for a patient with low libido?

Workup for Low Libido

A detailed history is the cornerstone of evaluation, followed by targeted physical examination and selective laboratory testing based on clinical suspicion—with morning testosterone measurement being the single most important initial test when hypogonadism is suspected. 1

Initial History Taking

The history should systematically explore multiple domains to distinguish psychogenic from organic causes:

Sexual History

• Duration and onset of decreased libido (sudden onset suggests psychogenic; gradual onset suggests organic) 2, 1
• Severity assessment using validated instruments such as the Sexual Desire Inventory-2 or Brief Sexual Symptom Checklist 1, 3
• Quality of spontaneous, self-stimulated, or morning erections (preserved erections suggest psychogenic etiology) 2
• Presence of other sexual dysfunctions including erectile dysfunction, premature ejaculation, or orgasmic difficulties 2, 4

Medical and Medication History

• Chronic conditions including diabetes, cardiovascular disease, hypertension, thyroid disorders, liver disease, and depression 5, 1
• Medication review, particularly antidepressants, antihypertensives, and psychoactive drugs that negatively impact libido 5, 6
• Alcohol consumption, recreational drug use, and smoking history 5
• Cancer treatment history if applicable 5, 1

Psychosocial Assessment

• Psychiatric conditions including generalized anxiety, depressive illness, psychosis, body dysmorphic disorder, and alcoholism 2, 1
• Relationship factors including marital satisfaction, partner sexual dysfunction (erectile dysfunction in male partners, vaginal dryness in female partners), and relational conflicts 1, 7
• Chronic stress, anxiety, and depression which interfere with motivational pathways of sexual response 1, 7

Physical Examination

For most patients, examination should be limited to the basic minimum unless history suggests specific abnormalities 2:

Essential Components

• Blood pressure measurement 2, 5
• Body mass index and body habitus to assess for obesity-associated hypogonadism 1
• Genital examination including testicular size, penile fibrosis, and retractable foreskin in men 2, 1
• Gynecologic examination in women to assess for vaginal atrophy, anatomic changes, and points of tenderness 5

Additional Examination When Indicated

• Signs of hypogonadism including virilization status and breast examination 1
• Cardiovascular assessment including cardiac auscultation, carotid bruits, and peripheral pulses if cardiovascular disease suspected 1
• Neurological examination if neurological disease suspected 2

Laboratory Investigations

Precise investigations depend on history and examination findings, with patients warranting extensive testing requiring specialist referral 2:

First-Line Laboratory Tests

Morning testosterone measurement (8-10 AM) is the single most important initial test when hypogonadism is clinically suspected 1, 8:

• Total testosterone on two separate occasions to confirm persistent hypogonadism (levels <300 ng/dL indicate hypogonadism) 1, 8
• Free testosterone by equilibrium dialysis or androgen index is preferred over total testosterone alone, as it can prevent unnecessary investigation in up to 50% of men with low total testosterone 2, 1
• Sex hormone-binding globulin (SHBG) to calculate free androgen index, particularly in obesity or diabetes where low SHBG may artificially lower total testosterone 1, 8

Additional Hormonal Studies (If Testosterone is Low)

• Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to distinguish primary (elevated LH/FSH) from secondary (low or low-normal LH/FSH) hypogonadism 1, 8
• Prolactin level if loss of libido with low testosterone, as hyperprolactinemia can cause secondary hypogonadism 5, 1

Metabolic and General Screening

• Thyroid function tests (TSH, free T4) if thyroid dysfunction suspected 5
• Fasting glucose or HbA1c to screen for diabetes 5, 1
• Lipid profile to assess cardiovascular risk 1
• Complete blood count for baseline hematocrit before potential testosterone therapy 1
• Complete metabolic panel if renal or hepatic impairment suspected 5

Prostate Assessment (Men Over 40)

• Prostate-specific antigen (PSA) and digital rectal examination as baseline before any hormone replacement therapy 2, 5

Validated Screening Questionnaires

Structured instruments should be used to quantify severity and facilitate discussion, but should not replace full patient evaluation and laboratory testing 1:

• Sexual Desire Inventory-2 for comprehensive assessment 1, 3
• Brief Sexual Symptom Checklist for Women as primary screening tool 5
• Female Sexual Function Index (FSFI) for more comprehensive evaluation in women 5
• International Index of Erectile Function or Sexual Health Inventory for Men in men 1

Referral Indications

Specialist referral is indicated in the following situations 2, 5:

• Young patients who have always had sexual difficulty
• Patients with history of trauma
• Abnormalities of testes or penis found on examination
• Initial screening tests indicating important abnormalities (multiple endocrine abnormalities, significantly elevated prolactin, very low testosterone with unclear etiology)
• Cancer survivors requiring specialized sexual health management

Common Pitfalls to Avoid

• Never diagnose hypogonadism based on symptoms alone without biochemical confirmation, as screening questionnaires have variable specificity and sensitivity 1
• Never measure testosterone at random times—always use morning measurements (8-10 AM) due to diurnal variation 1, 8
• Never rely on single testosterone measurement—always confirm with repeat testing due to assay variability 1, 8
• Never assume organic cause without exploring psychosocial factors, as relationship dissatisfaction is the most common factor in depressed desire 6
• Always measure free testosterone or SHBG in borderline cases, particularly in obesity or diabetes, as total testosterone alone may miss true hypogonadism 2, 1